1. Field of the Invention
The present invention relates to a recording head that includes a plurality of recording chips equipped with recording element arrays, wherein the plurality of recording chips are partly overlapped and mutually connected in a direction parallel to the recording element arrays. When an image recording apparatus records an image on a recording medium, the image recording apparatus generates dot data for the recording head.
2. Description of the Related Art
Image recording apparatuses are generally configured to record images (including characters and marks) on recording media (e.g., sheets) based on recording information. The image recording apparatuses can be classified into an inkjet type, a wire dot type, a thermal type, a laser beam type, or another type, according to the type of recording.
An inkjet type recording apparatus (i.e., an inkjet recording apparatus) includes an inkjet recording head (hereinafter, simply referred to as a “recording head”), which can serve as a recording unit. The recording head has recording elements that can discharge ink toward a recording medium to record an image.
A serial type inkjet recording apparatus can perform a recording operation with a recording head that performs scanning in a main scanning direction perpendicular to a conveyance direction of a recording medium (i.e., a sub scanning direction). The serial type inkjet recording apparatus causes a recording head to move along a recording medium to record an image on the recording medium.
More specifically, each time when the recording head finishes a recording operation corresponding to one complete main scanning, the serial type inkjet recording apparatus conveys the recording medium by a predetermined amount in the sub scanning direction. The serial type inkjet recording apparatus repeats the above-described operation to complete the recording on the entire region of the recording medium.
A full line type inkjet recording apparatus includes a recording head whose recording width is comparable to the width of a recording medium. The full line type inkjet recording apparatus is configured to continuously perform a recording operation for one complete line without moving the recording head, while conveying the recording medium. The full line type inkjet recording apparatus is advantageous in speedily accomplishing image formation processing, and can be adequately used as a recording apparatus dedicated to the on demand type recording services, whose needs are recently increasing, for example, as discussed in Japanese Patent Application Laid-Open No. 2002-292859.
However, in manufacturing the recording head to be incorporated in the above-described full line type recording apparatus, it is difficult to accurately produce all of the inkjet recording elements without any defects, so as to be sequentially disposed in a long length comparable to the entire width of a recording region of a recording medium.
For example, when the full line type recording apparatus performs recording on a sheet of A3 size paper so as to realize a resolution level of 1200 dpi, a full line type recording head is required to include approximately 14 thousands of recording elements (approximately 280 mm in recording width). It is generally difficult to manufacture all of such numerous recording elements without any defects. Even if the manufacturing of the above-described recording head can be successfully accomplished, an efficiency percentage may be low and manufacturing costs may increase.
For the reasons described above, a long connected head is proposed as a prospective full line type recording head. The connected head is a recording head including a plurality of recording element arrays, each including a plurality of recording elements, which are continuously or sequentially disposed in the direction parallel to the recording element arrays.
More specifically, the connected head is a recording head including a plurality of short heads (i.e., the heads used in the above-described serial type inkjet recording apparatus), which are connected in the direction parallel to the recording element arrays to realize an elongated head configuration. Similarly, the serial type recording apparatus can use a long recording head to perform recording if the long recording head can be realized by the above-described connecting configuration.
However, an image generated by the connected head may include undesirable streaks in a region corresponding to a connected portion extending between two recording element arrays where edges of two recording element arrays are overlapped with each other. In general, such undesirable streaks appear in an image region corresponding to a connected portion extending between two recording element arrays when an impact position of a coloring material recorded by a recording element array deviates from a correct position. For example, the impact position of a coloring material deviates from the correct position when the mounting location of a recording element array deviates from a predetermined position, or when the recording element array is mounted in an inclined state (i.e., when the recording head is mounted in an inclined state).
FIG. 1 illustrates a positional relationship between a recording head 101, which is in an ideal state where no deviation occurs in impact position of ink, and a dot layout pattern that can be recorded by respective recording element arrays (i.e., a first recording element array 102 and a second recording element array 103). A right-side schematic illustration in FIG. 1 is an example pattern of ideal dots that do not generate any streaks appearing in an image region corresponding to a connected portion extending between two recording element arrays.
In FIG. 1, a direction X indicates a conveyance direction of a recording medium and a direction Y indicates a direction perpendicular to the direction X. Each of the recording element arrays constituting the recording head 101 (i.e., the first recording element array 102 and the second recording element array 103) extends in the direction Y. In general, the size of each dot is sufficiently large so that neighboring dots can be overlapped with each other. However, for the sake of convenience, the dots illustrated in FIG. 1 are smaller ones.
On the other hand, FIG. 2 illustrates an example pattern of dots in a case where amounting location of the second recording element array 103 deviates from the ideal position, according to which streaks are generated in an image region corresponding to a connected portion extending between two recording element arrays due to a deviation in ink impact position caused by the mounting deviation of the second recording element array 103.
In FIG. 2, the mounting location of the second recording element array 103 relative to the first recording element array 102 is shifted from an ideal position toward a positive direction in the direction Y. Therefore, the density of dots decreases in the image region corresponding to the connected portion extending between two recording element arrays. In other words, white streaks appear in the image region corresponding to the connected portion extending between two recording element arrays.
FIG. 3 illustrates an example pattern of dots in a case where the recording head 101 is inclined, according to which streaks are generated in an image region corresponding to a connected portion extending between two recording element arrays due to a deviation in ink impact position. In FIG. 3, the recording head 101 is inclined in the clockwise direction relative to the vertical direction of an XY plane.
As a result, direction Y positions of the dots recorded by the second recording element array 103 are shifted toward a positive direction relative to direction Y positions of the dots recorded by the first recording element array 102. Therefore, the dot density decreases in an image region corresponding to a connected portion extending between two recording element arrays. In other words, white streaks appear in the image region corresponding to the connected portion extending between two recording element arrays.
There are some conventional methods available to prevent the above-described streaks from appearing in an image region corresponding to a connected portion extending between two recording element arrays. For example, a conventional method for accurately arranging the recording chips in the connected portion is available. This method can reduce a deviation in pitch of respective recording elements.
Further, there is another conventional method for reducing or weakening the streaks appearing in the image region corresponding to the connected portion extending between two recording element arrays by controlling the number of dots to be recorded by each recording element array that constitutes the connected portion as illustrated in FIG. 1.
However, if the chip arrangement in the connected portion is accurately performed, manufacturing costs increase significantly. Further, if a correction is performed by appropriately increasing or reducing the number of recording dots to be used by each recording element array that constitutes the connected portion, it is necessary to individually determine an appropriate correction amount according to each gradation for all pixels. Therefore, a complicated configuration is required.